The present invention relates to a seat belt retractor with a frame, a spool rotatably mounted in the frame and a blocking mechanism for selectively blocking rotation of the spool to prevent belt webbing from being withdrawn from the spool.
Seat belt retractors for use in vehicles are mounted to some part of the vehicle bodywork at a location depending on the type of vehicle, the seat belt system used and the particular seat configuration. For reasons of optical appearance and protection, seat belt retractors are accommodated within some hollow space of the vehicle bodywork, and the belt webbing passes through an opening in an internal wall of the vehicle bodywork. For example, a seat belt retractor of a conventional three-point safety belt system associated with a front seat is typically accommodated within the B pillar of the vehicle, and the belt webbing is guided within the B pillar upwardly to and through a deflection ring.
Typically, a single screw bolt is used to attach the retractor frame to the vehicle bodywork. When the belt webbing is heavily tensioned such as in a vehicle crash, the tension load acting on the spool is transmitted to the retractor frame and then to the vehicle bodywork by means of the screw bolt. It is thus clear that the screw bolt has a critical function in assuring that the forces acting on the retractor frame are transmitted to and supported by the vehicle bodywork.
When the belt retractor is mounted at a hidden location within the vehicle, a visual verification of its mounting condition is usually impossible.
To ensure that an incomplete mounting condition where the screw bolt is not or not completely screwed in can be reliably determined, the present invention provides a seat belt retractor with a belt spool that remains b locked until the mounting procedure whereby the retractor frame is attached to the vehicle bodywork, is completed. It is thus easy to check the mounting condition by simply pulling on the belt webbing. No belt webbing can be withdrawn from the retractor as long as the mounting procedure is not completed.
Specifically, the present invention provides a seat belt retractor having a frame, a spool rotatably mounted in the frame, a blocking mechanism for selectively blocking rotation of the spool to prevent belt webbing from being withdrawn from the spool, and mounting means for mounting the retractor to a vehicle body part. In accordance with the invention, mounting condition sensing means are functionally inserted between the blocking mechanism and mounting means and effective to maintain the blocking mechanism in a blocking condition if and as long as an incomplete mounting condition is detected. In the preferred embodiment where the mounting means includes a bolt for attachment of the retractor frame to the vehicle body part, the mounting condition sensing means is acted on by the bolt. Thus, the inventive belt reactor can be attached in the vehicle by a conventional mounting procedure using a screw bolt. In the preferred embodiment, the mounting condition sensing means comprises a sensing member such as a slider adapted to be contacted by a front end of the bolt and to be pushed into a predetermined position by the bolt when a completed mounting condition is detected. A similar slider has been in use on belt retractors with a pyrotechnic pretensioner drive with mechanical activator as a component of a safe transport system for disabling the activator during shipment and handling. In the latter case, the invention also permits to verify easily that the pretensioner drive is enabled after the mounting procedure is completed.
Further features of the invention will become apparent from the following description with reference to the drawings. In the drawings,